Two years prior to the introduction of the Mercedes-Benz “Ponton” models, the Type 300 “Adenauer” limousines were already being built by Daimler-Benz. They were different in many respects from the “Ponton” models, but to the casual observer, they shared a similar outward appearance. The main structural difference was that the Type 300 had a separate body and frame. These traditionally luxurious and yet technologically advanced super-cars were primarily used by governments, heads of state, royalty and other members of the heavy wallet brigade. Their engineering, luxury, high price and low production rates placed them at the very top of the already exclusive Daimler-Benz passenger vehicle hierarchy during the 1951-1962 period.

Mercedes-Benz first unveiled the W186, 300 series sedan (no letter designation) and cabriolet 4-door model at the 1951 Paris exhibition auto show. It's unique appearance and features, in comparison to previous post war models, were a huge success, gaining instant appeal by State governments, celebrities, and wealthy businessmen. Features included the X frame chassis of prior models, a 6 cylinder overhead valve carburated engine to compensate for 2+1/2 ton weight, central lubrication system of the 170 model, swing axle, and rear load leveler.